Allowance for Credit Losses, Credit Quality and Other - Summary of Most Recent Analysis Performed, Risk Category of Loans by Class of Loans and Writeoffs (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2024	Dec. 31, 2023
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	$ 430,301	$ 2,138,730
Year Two	2,131,418	3,341,500
Year Three	3,310,602	2,083,044
Year Four	1,991,010	1,132,926
Year Five	1,013,542	872,429
Prior	3,636,939	2,908,528
Revolving Loans Amortized Cost Basis	1,999,861	1,947,571
Total	14,513,673	14,424,728
Writeoffs, Year One	772	3,252
Writeoffs, Year Two	119	490
Writeoffs, Year Three	132	1,351
Writeoffs, Year Four	1,034	1,072
Writeoffs, Year Five	114	2,878
Writeoffs, Prior	452	6,357
Writeoffs, Revolving	1,355	655
Writeoffs, Total	3,978	16,055
Commercial real estate loans
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	233,110	930,022
Year Two	1,040,059	2,146,390
Year Three	2,100,729	1,262,133
Year Four	1,231,875	626,807
Year Five	532,587	481,164
Prior	2,301,263	1,905,250
Revolving Loans Amortized Cost Basis	845,515	816,391
Total	8,285,138	8,168,157
Commercial real estate loans \| Non-farm/non-residential
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	91,081	388,831
Year Two	489,474	1,150,598
Year Three	1,103,794	830,588
Year Four	852,764	491,298
Year Five	422,460	404,822
Prior	2,086,282	1,747,135
Revolving Loans Amortized Cost Basis	571,110	536,682
Total	5,616,965	5,549,954
Writeoffs, Year One	0	0
Writeoffs, Year Two	0	0
Writeoffs, Year Three	0	0
Writeoffs, Year Four	750	0
Writeoffs, Year Five	1	1,826
Writeoffs, Prior	351	502
Writeoffs, Revolving	0	0
Writeoffs, Total	1,102	2,328
Commercial real estate loans \| Construction/land development
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	121,343	501,215
Year Two	505,026	926,208
Year Three	929,433	384,657
Year Four	336,539	88,901
Year Five	71,377	55,857
Prior	124,043	81,216
Revolving Loans Amortized Cost Basis	242,794	254,993
Total	2,330,555	2,293,047
Writeoffs, Year One	0	0
Writeoffs, Year Two	0	2
Writeoffs, Year Three	0	168
Writeoffs, Year Four	0	5
Writeoffs, Year Five	1	0
Writeoffs, Prior	0	88
Writeoffs, Revolving	0	0
Writeoffs, Total	1	263
Commercial real estate loans \| Agricultural
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	20,686	39,976
Year Two	45,559	69,584
Year Three	67,502	46,888
Year Four	42,572	46,608
Year Five	38,750	20,485
Prior	90,938	76,899
Revolving Loans Amortized Cost Basis	31,611	24,716
Total	337,618	325,156
Writeoffs, Year One	0	0
Writeoffs, Year Two	0	0
Writeoffs, Year Three	0	0
Writeoffs, Year Four	0	0
Writeoffs, Year Five	0	1
Writeoffs, Prior	0	6
Writeoffs, Revolving	0	0
Writeoffs, Total	0	7
Residential real estate loans \| Residential 1-4 family
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	71,946	261,784
Year Two	239,035	409,197
Year Three	424,678	300,563
Year Four	294,679	171,122
Year Five	165,656	111,327
Prior	493,485	403,729
Revolving Loans Amortized Cost Basis	210,495	186,538
Total	1,899,974	1,844,260
Writeoffs, Year One	0	0
Writeoffs, Year Two	1	29
Writeoffs, Year Three	68	28
Writeoffs, Year Four	0	73
Writeoffs, Year Five	25	13
Writeoffs, Prior	65	126
Writeoffs, Revolving	0	0
Writeoffs, Total	159	269
Residential real estate loans \| Multifamily residential
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	424	3,983
Year Two	3,996	87,012
Year Three	106,711	107,301
Year Four	75,459	108,702
Year Five	108,441	39,815
Prior	105,987	74,564
Revolving Loans Amortized Cost Basis	14,908	14,359
Total	415,926	435,736
Total real estate
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	305,480	1,195,789
Year Two	1,283,090	2,642,599
Year Three	2,632,118	1,669,997
Year Four	1,602,013	906,631
Year Five	806,684	632,306
Prior	2,900,735	2,383,543
Revolving Loans Amortized Cost Basis	1,070,918	1,017,288
Total	10,601,038	10,448,153
Writeoffs, Year One	0	0
Writeoffs, Year Two	1	31
Writeoffs, Year Three	68	196
Writeoffs, Year Four	750	78
Writeoffs, Year Five	27	1,840
Writeoffs, Prior	416	722
Writeoffs, Revolving	0	0
Writeoffs, Total	1,262	2,867
Consumer
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	47,780	255,930
Year Two	247,337	257,588
Year Three	250,968	216,645
Year Four	210,945	109,981
Year Five	104,212	110,406
Prior	298,983	200,071
Revolving Loans Amortized Cost Basis	3,003	3,069
Total	1,163,228	1,153,690
Writeoffs, Year One	0	0
Writeoffs, Year Two	12	51
Writeoffs, Year Three	39	44
Writeoffs, Year Four	26	98
Writeoffs, Year Five	87	63
Writeoffs, Prior	34	263
Writeoffs, Revolving	0	25
Writeoffs, Total	198	544
Commercial and industrial
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	54,767	619,371
Year Two	540,127	385,376
Year Three	376,109	156,919
Year Four	140,432	88,094
Year Five	76,325	114,522
Prior	376,598	276,677
Revolving Loans Amortized Cost Basis	720,417	684,032
Total	2,284,775	2,324,991
Writeoffs, Year One	0	0
Writeoffs, Year Two	106	407
Writeoffs, Year Three	25	1,110
Writeoffs, Year Four	258	894
Writeoffs, Year Five	0	911
Writeoffs, Prior	2	5,369
Writeoffs, Revolving	1,355	466
Writeoffs, Total	1,746	9,157
Agricultural & other
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	22,274	67,640
Year Two	60,864	55,937
Year Three	51,407	39,483
Year Four	37,620	28,220
Year Five	26,321	15,195
Prior	60,623	48,237
Revolving Loans Amortized Cost Basis	205,523	243,182
Total	464,632	497,894
Writeoffs, Year One	772	3,252
Writeoffs, Year Two	0	1
Writeoffs, Year Three	0	1
Writeoffs, Year Four	0	2
Writeoffs, Year Five	0	64
Writeoffs, Prior	0	3
Writeoffs, Revolving	0	164
Writeoffs, Total	772	3,487
Risk rating 1 \| Commercial real estate loans \| Non-farm/non-residential
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	0	0
Year Two	0	0
Year Three	0	0
Year Four	0	0
Year Five	0	232
Prior	342	116
Revolving Loans Amortized Cost Basis	91	55
Total	433	403
Risk rating 1 \| Commercial real estate loans \| Construction/land development
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	0	0
Year Two	0	0
Year Three	0	10
Year Four	10	0
Year Five	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Total	10	10
Risk rating 1 \| Commercial real estate loans \| Agricultural
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	700	0
Year Two	0	1,605
Year Three	1,550	0
Year Four	0	0
Year Five	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Total	2,250	1,605
Risk rating 1 \| Residential real estate loans \| Residential 1-4 family
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	0	0
Year Two	0	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior	96	144
Revolving Loans Amortized Cost Basis	2	2
Total	98	146
Risk rating 1 \| Residential real estate loans \| Multifamily residential
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	0	0
Year Two	0	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Total	0	0
Risk rating 1 \| Total real estate
Financing Receivable Allowance For Credit Losses [Line Items]
Year One		1,195,789
Year Two		2,642,599
Year Three		1,669,997
Year Four		906,631
Year Five		632,306
Prior		2,383,543
Revolving Loans Amortized Cost Basis		1,017,288
Total		10,448,153
Risk rating 1 \| Consumer
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	2,232	5,195
Year Two	4,108	2,952
Year Three	2,526	2,002
Year Four	1,834	839
Year Five	769	355
Prior	1,238	1,114
Revolving Loans Amortized Cost Basis	1,529	1,580
Total	14,236	14,037
Risk rating 1 \| Commercial and industrial
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	678	3,757
Year Two	1,729	918
Year Three	860	1,120
Year Four	816	236
Year Five	231	121
Prior	20,920	20,835
Revolving Loans Amortized Cost Basis	12,287	12,644
Total	37,521	39,631
Risk rating 1 \| Agricultural & other
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	427	408
Year Two	402	131
Year Three	120	16
Year Four	16	105
Year Five	105	0
Prior	0	2
Revolving Loans Amortized Cost Basis	331	563
Total	1,401	1,225
Risk rating 2 \| Commercial real estate loans \| Non-farm/non-residential
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	0	0
Year Two	0	0
Year Three	0	0
Year Four	0	0
Year Five	0	111
Prior	109	0
Revolving Loans Amortized Cost Basis	0	0
Total	109	111
Risk rating 2 \| Commercial real estate loans \| Construction/land development
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	0	759
Year Two	138	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior	179	186
Revolving Loans Amortized Cost Basis	0	0
Total	317	945
Risk rating 2 \| Commercial real estate loans \| Agricultural
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	0	247
Year Two	245	0
Year Three	0	1,936
Year Four	1,908	0
Year Five	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Total	2,153	2,183
Risk rating 2 \| Residential real estate loans \| Residential 1-4 family
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	0	259
Year Two	867	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior	14	20
Revolving Loans Amortized Cost Basis	1	1
Total	882	280
Risk rating 2 \| Residential real estate loans \| Multifamily residential
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	0	0
Year Two	0	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Total	0	0
Risk rating 2 \| Consumer
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	0	0
Year Two	0	0
Year Three	0	0
Year Four	0	0
Year Five	0	126
Prior	170	54
Revolving Loans Amortized Cost Basis	0	0
Total	170	180
Risk rating 2 \| Commercial and industrial
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	0	174
Year Two	160	1,293
Year Three	1,221	220
Year Four	208	12
Year Five	10	164
Prior	20	218
Revolving Loans Amortized Cost Basis	1,130	963
Total	2,749	3,044
Risk rating 2 \| Agricultural & other
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	71	396
Year Two	308	28
Year Three	28	1
Year Four	1	0
Year Five	0	1,181
Prior	1,216	100
Revolving Loans Amortized Cost Basis	743	693
Total	2,367	2,399
Risk rating 3 \| Commercial real estate loans \| Non-farm/non-residential
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	83,363	305,742
Year Two	331,573	584,860
Year Three	594,821	568,413
Year Four	581,031	243,177
Year Five	241,146	216,746
Prior	1,121,885	934,111
Revolving Loans Amortized Cost Basis	437,309	440,414
Total	3,391,128	3,293,463
Risk rating 3 \| Commercial real estate loans \| Construction/land development
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	103,471	300,941
Year Two	338,932	499,984
Year Three	491,298	130,342
Year Four	113,870	62,134
Year Five	50,553	22,656
Prior	70,571	56,180
Revolving Loans Amortized Cost Basis	47,987	44,603
Total	1,216,682	1,116,840
Risk rating 3 \| Commercial real estate loans \| Agricultural
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	12,689	30,252
Year Two	35,840	43,291
Year Three	43,636	22,919
Year Four	20,758	25,992
Year Five	24,044	10,678
Prior	48,712	43,284
Revolving Loans Amortized Cost Basis	26,975	20,104
Total	212,654	196,520
Risk rating 3 \| Residential real estate loans \| Residential 1-4 family
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	68,236	246,462
Year Two	222,450	366,149
Year Three	374,959	241,985
Year Four	238,269	145,339
Year Five	140,564	93,751
Prior	399,083	324,569
Revolving Loans Amortized Cost Basis	123,952	122,950
Total	1,567,513	1,541,205
Risk rating 3 \| Residential real estate loans \| Multifamily residential
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	424	3,314
Year Two	3,300	9,827
Year Three	25,242	37,755
Year Four	37,413	44,407
Year Five	44,195	31,436
Prior	81,998	53,068
Revolving Loans Amortized Cost Basis	6,867	6,537
Total	199,439	186,344
Risk rating 3 \| Consumer
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	44,644	240,897
Year Two	230,405	245,543
Year Three	238,893	211,312
Year Four	206,923	108,009
Year Five	102,296	108,063
Prior	289,483	191,220
Revolving Loans Amortized Cost Basis	1,196	1,264
Total	1,113,840	1,106,308
Risk rating 3 \| Commercial and industrial
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	21,943	487,896
Year Two	475,638	272,608
Year Three	267,003	78,507
Year Four	73,719	50,340
Year Five	52,985	77,761
Prior	248,283	170,610
Revolving Loans Amortized Cost Basis	227,129	227,043
Total	1,366,700	1,364,765
Risk rating 3 \| Agricultural & other
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	17,995	52,758
Year Two	51,938	45,796
Year Three	40,941	31,378
Year Four	30,317	26,918
Year Five	25,416	3,059
Prior	44,812	43,984
Revolving Loans Amortized Cost Basis	140,789	145,419
Total	352,208	349,312
Risk rating 4 \| Commercial real estate loans \| Non-farm/non-residential
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	7,718	83,089
Year Two	157,901	557,540
Year Three	499,982	242,217
Year Four	251,916	224,378
Year Five	157,181	149,258
Prior	710,773	590,864
Revolving Loans Amortized Cost Basis	133,521	95,360
Total	1,918,992	1,942,706
Risk rating 4 \| Commercial real estate loans \| Construction/land development
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	17,872	198,874
Year Two	165,321	417,244
Year Three	426,339	252,602
Year Four	220,985	22,713
Year Five	19,545	32,342
Prior	52,325	24,527
Revolving Loans Amortized Cost Basis	193,864	209,063
Total	1,096,251	1,157,365
Risk rating 4 \| Commercial real estate loans \| Agricultural
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	7,297	9,477
Year Two	9,474	24,688
Year Three	22,316	20,358
Year Four	18,238	19,532
Year Five	13,622	7,873
Prior	40,145	32,692
Revolving Loans Amortized Cost Basis	4,636	4,612
Total	115,728	119,232
Risk rating 4 \| Residential real estate loans \| Residential 1-4 family
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	3,710	14,992
Year Two	14,286	37,444
Year Three	43,663	55,406
Year Four	52,466	21,240
Year Five	20,855	13,313
Prior	76,831	67,084
Revolving Loans Amortized Cost Basis	85,756	62,356
Total	297,567	271,835
Risk rating 4 \| Residential real estate loans \| Multifamily residential
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	0	669
Year Two	696	77,185
Year Three	81,319	69,546
Year Four	38,046	64,295
Year Five	64,246	8,116
Prior	23,736	18,490
Revolving Loans Amortized Cost Basis	8,041	7,822
Total	216,084	246,123
Risk rating 4 \| Consumer
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	904	9,597
Year Two	7,573	7,534
Year Three	8,067	2,479
Year Four	1,015	69
Year Five	49	109
Prior	4,911	6,073
Revolving Loans Amortized Cost Basis	255	214
Total	22,774	26,075
Risk rating 4 \| Commercial and industrial
Financing Receivable Allowance For Credit Losses [Line Items]
Year One	32,124	115,025
Year Two	50,433	34,474
Year Three	33,941	55,812
Year Four	44,843	33,000
Year Five	19,245	27,189
Prior	85,821	71,854

Allowance for Credit Losses, Credit Quality and Other - Summary of Most Recent Analysis Performed, Risk Category of Loans by Class of Loans and Writeoffs (Detail) - USD ($)
$ in Thousands